Mechanical pencil

ABSTRACT

A throwaway repeater-type pencil cartridge employs a molded plastic magazine, a molded plastic lead advancing clutch and a tubular point clutch assemblable by the mere dropping of the parts one by one into the casing.

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References Cited UNITED STATES PATENTS 7 77 6 66 1 ll 0 00 4 44 n m mm"mu" mAmm m m m r N r mGmm f. E6 a w PD GS 9 0 6 65 9 99 1 ll ll 4 78Primary Examiner-Lawrence Charles Attorney-Fidler, Bradley, Patnaude &Laza ABSTRACT: A throwaway repeater-type pencil cartridge employs amolded plastic magazine, a molded plastic lead advancing clutch and atubular point clutch assemblable by the mere dropping of the parts oneby one into the casing.

\ i tilt iii lilillllli illlllll WWI a J L mmj PW m m Mn ED M N4, mm imm s MECHANICAL PENCIL The present invention relates to a mechanicalpencil having a repeater-type step-by-step lead advancing means whereina plurality of lead rods contained in the pencil are fed seriatim to thewriting point in response to repeated actuation of the reciprocal leadfeed mechanism. More particularly, this invention relates to a mechanismof this type employing more simplified components which may be assembledin a more facile manner.

Step-by-step lead advancing mechanisms as known in the prior art andexemplified by U.S. Pat. No. 2,528,328 to Baker et al. and U.S. Pat. No.2,514,6l to Schweitzer are relatively expensive to manufacture becauseof the complex nature of their components and the difficulty ofassembly. As a consequence, pencils employing this type of mechanismhave always been relatively expensive compared to the screw typemechanical pencil. However, the step-by-step lead feed mechanism hasseveral important operating advantages over the screw-type and,therefore, it would be desirable to provide a new and improvedstep-by-step lead feed mechanism wherein the components would beinexpensive compared to those of the prior art and wherein the mechanismis more compatible with automated assembly processes.

Therefore, an object of the present invention is to provide a new andimproved mechanical pencil construction.

Another object of the present invention is to provide a new and improvedstep-by-step lead advancing mechanism using relatively inexpensivecomponents.

A further object of the present invention is to provide a new andimproved lead advancing mechanism wherein the components thereof may beformed of plastic in a molding opera tion.

A still further object of the present invention is to provide a new andimproved step-by-step lead advancing mechanism wherein the componentscan be facilely assembled together.

A still further object of the present invention is to provide a new andimproved throwaway-type cartridge which includes a supply of lead rodsand a step-by-step advancing mechanism for feeding the lead rods fromthe supply chamber to the writing tip.

Other objects and advantages and a better understanding of the inventionmay be had by reference to the following detailed description of apreferred embodiment thereof taken in connection with the accompanyingdrawing wherein:

FIG. 1 is a fragmentary longitudinally sectioned view of a throwawaymechanical pencil cartridge embodying the present invention and showingthe mechanism in an at rest writing position;

FIG. 2 is a longitudinally sectioned view similar to FIG. 1 but showingthe advancing mechanism in a forwardmost position;

FIG. 3 is an exploded perspective view of a portion of the leadadvancing mechanism of the present invention; and

FIG. 4 is a sectional view taken along the line 4-4 of FIG. 1.

Referring now to the drawings and particularly to FIG. 1 thereof, thereis shown a self-contained throwaway-type pencil cartridge which isadapted to be used in a writing instrument housing such as thatdisclosed in U.S. Pat. No. 3,205,863 to Rhoades, which patent isassigned to the same assignee as is the present invention.

The cartridge 10 includes a shell 12 which may be formed of metal butmight also be formed of plastic and which is tubular in constructionhaving a plurality of progressively necked down portions 14, 15, 16 and17. A generally tubular magazine 18 which is preferably molded ofplastic defines a lead supplying chamber 19 and is slidably disposed inthe main body section of the casing 12. After the chamber 19 has beenfilled with a supply of lead sticks or rods, a plug 21 is inserted intothe rearward end thereof and secured in place. An annular flange 23 isprovided at the rearward end of the magazine 18 and a rearwardly facingannular shoulder 25 is provided on the outer surface of the magazine 18in spaced relationship from the flange 23 to cooperate with a pluralityof reentrant tabs 27 at the rear end of the casing 12. These tabs 27 arebent inwardly after the magazine and the other feed mechanism has beenplaced within the shell 12 to prevent disassembly of the mechanism fromthe shell.

The magazine 18 further includes a forwardly extending elongated tubularsection 29 having a centrally disposed aperture 31 therein whosediameter slightly exceeds that of the lead rods 33 with which the pencilis used. The lower wall 35 of the chamber 19 converges toward theopening 31 so that as the rear end of the lead rod 33 being feddownwardly through the instrument reaches the rear end of the feedopening 31 another lead rod contained in the chamber 19 willautomatically follow it into the advancing mechanism. As best shown inFIGS. 1 and 3, the tubular section 29 is provided with a pair ofdiametrically opposed slots 36 and the forward ends of the thus formedparts of tubular section 29 are pointed at the distal ends 37.

Slidably disposed over the forward tubular section 29 of the magazine 18is a lead advancing clutch 40 including a rearwardly disposed annularbody portion 42 which loosely fits over the tubular section 29 and holdsthe clutch in place thereon.

The lead advancing clutch 40 further includes a pair of integrallyformed fingers 43 and 44 which respectively include external cammingsurfaces 45 and 46 and internally disposed lead engaging surfaces 47 and48 which, as best shown in FIG. 4, are semicylindrical. As more fullydescribed hereinafter, when the magazine 18 is moved downwardly withinthe casing 12 to actuate the lead feeding mechanism, the clutch fingers43 and 44 are moved downwardly and the cam surfaces 45 and 46 engage theannular shoulder 50 on the inner wall of the casing between the mainbody portion and the necked down portion 14 thereby to cam the fingers43 and 44 radially inwardly so that the inner surfaces 47 and 48 finnlyengage and grip the lead rod 33 contained therein to prevent movement ofthe lead rod relative to the advancing clutch 40.

A lead guide tube and point collet 52 extends through the forwardportion of the casing 12 and is removably secured at its rearward end tothe forward end of the tubular section 29 of the magazine 18. Moreparticularly, the member 52 has an annular groove 53 near its rearwardend, and internal beads 54 on the forwardly extending fingerlikeportions of the magazine 18 are snap-fitted therein to removably securethe guide tube and point collet 52 to the magazine 18. The forward endof the member 52 is provided with a plurality of Iongitudinal slitswhich separate the forward end into a plurality of jaws 56 whichcooperate with the internal wall of the forward portion 17 of the casing12 to tightly grip the lead rod 33 contained therein when the pointcollet is in its rearmost assembled position as shown in FIG. 1. Thebore of the collet member 52 is slightly larger than the lead rod 33.The jaws 56 are resiliently biased in an inward condition slightlysmaller in aperture than the diameter of the lead rod 33 providingsufficient friction to retain the lead rod during forward movement ofthe jaws 56 from the reduced section 17 of the casing as shown in FIG.2. With no lead in the pencil, thejaws 56 have a minimum externaldiameter less than the internal diameter of the most reduced section 17of the casing 12 to permit assembly of the collet into the forward endof the casing from the rearward end thereof.

Mounted over the rearward end of the guide tube and point collet 52 is aguide bushing 58 having a rearward tubular portion loosely fitted overthe forward end of the tubular projection 29 in the magazine 18 andhaving a necked down intermediate section 60 defining a forwardly facingannular shoulder 62 against which the rear end of a return spring 64abuts. The bushing 58 further includes a forward portion 66 of stillgreater reduced diameter to define an internal annular shoulder 68 whichabuts a forwardly facing annular shoulder 70 on the guide tube and pointcollet 52. As shown, in FIG. 1, the forward end of the return spring 64abuts against an internal annular shoulder 72 provided intermediate thecasing sections 14 and 15.

The cartridge including the lead advancing mechanism of the presentinvention is adapted to be easily and quickly assembled either by handor by automated assembly equipment. In order to assemble this cartridge,the coil spring 64 is simply dropped into the rear end of the casing I2so that it falls against the shoulder 72. The bushing 53 may then bedropped into the rear end of the casing 12 so that it falls into therear end of the spring 64 and thereafter the lead guide tube and pointcollet 52 is dropped into place so that its shoulder 70 abuts againstthe annular shoulder 68 on the bushing 58. The lead advancing clutch 40may then be dropped into place in the casing 12 and finally the magazine18 is inserted. It is, of course, necessary that the slots 36 in theforward end of the magazine be aligned with the fingers 43 and 44 of thelead advancing clutch. This is accomplished automatically by virtue ofthe fact that the rearward ends 74 and 76, respectively, of the clutchfingers 43 and 44 are longitudinally staggered and the forward ends 37of the tubular section 29 of the magazine 18 are pointed. As a result,the magazine will rotate relative to the clutch when the pointedsurfaces 37 engage the lug surfaces 74 and 76. Accordingly, by merelydropping the parts one by one into the shell 12, the individualcomponents automatically occupy the relative positions shown in FIG. I.Thereafter, the magazine 18 is pressed forwardly so that the shoulder 25thereon lies below the tabs 27, on the shell 12. The tabs are thenpressed into place to maintain the unit in an assembled condition.

OPERATION When the mechanical pencil cartridge has been assembled asdescribed above, one of the lead rods 33 contained in the lead supplychamber 119 will slide down the sloping wall 35 at the bottom of themagazine chamber and its forward end will fall into the hole 31 throughthe forward tubular section 29 to some extent as determined by themisalignment of the apertures 31 and the bore through the guide tube 52.Actuation of the mechanism by depressing the magazine 18 into the casing12 will result in the following operation. The lead guide and pointcollet 52 will, because of the snap fit between the beads 54 and thegroove 53, move forwardly so that the jaws 56 relax. The forwardlyfacing annular shoulder 30 of the magazine 18 thereafter engages therear end of the advancing clutch 40, and the camming surfaces 45 and 46on the clutch fingers are moved against the shoulder 50. Continueddepression of the magazine causes the fingers 43 and 44 to be cammedinwardly to engage the lead rod 33, and the clutch 40 moves forwarduntil the underside of the annular flange 23 engages the end of thecasing 12 as shown in FIG. 2. Since the point collet 52 is already in aforward position with the jaws 56 relaxed, the lead rod is held in placeprimarily by the fingers 43 and 44 on the clutch 40. Therefore, when themagazine is released and the spring 64 expands, the point collet 52moves back into the shell 112. However, the clutch 40 is frictionallyheld in the tubular section I4 of the shell l2 and thus holds the leadrod 33 in a fixed position related to the shell. When, during its returnmovement, the rear end of the point collet 52 engages the forward endsof the clutch fingers 43 and 44 the clutch is moved out of the section14 and the fingers 43 and 44 expand away from the lead rod 33. By thistime the jaws 56 have retracted into a lead holding position. It maythen be seen that the length of lead which is advanced upon e eachcomplete actuation of the advancing mechanism is the distance throughwhich the advancing clutch 40 may move relative to the point collet 52.

While the present invention has been described in connection with aparticular embodiment thereof, it will be understood that many changesand modifications may be made by those skilled in the art withoutdeparting from the invention. Therefore, by the appended claims, it isintended to cover all such changes and modifications as come within thetrue spirit and scope of the invention.

Iclaim:

1. In a mechanical pencil of the step-by-step propulsion type, thecombination com rising an elongated, integral, tu ular casing having anecked down front end,

a lead magazine element having a hollow, cylindrical main body portionfor holding a plurality of lead rods and a forwardly extending,generally tubular section of reduced diameter provided with a pluralityof longitudinal slots extending to and opening at the forward end toprovide a plurality of forwardly extending resilient fingers,

an advancing clutch including a collar surrounding said fingers andslidable thereon and having a plurality of lead engaging clutch fingersrespectively disposed in said slots,

an integral lead guide and point clutch element having an internaldiameter larger than but approximating the external diameter of saidlead rods to permit said rods to slide therein and therethrough,

said lead guide and point clutch element being mounted in said casingforwardly of said advancing clutch and having an enlarged forward endincluding a plurality of point engaging resilient jaws located forwardlyof the front end of said casing,

the external diameter of said enlarged forward end exceeding theinternal diameter of said necked down front end of said casing, therebypreventing the passage of said front end through said front end of saidcasing,

the rear end of said lead guide and point clutch element beingsnap-fitted into the forward end of said resilient fingers with the holethrough said lead guide and point clutch in alignment with the holethrough said tubular section of said magazine to permit assembly of saidlead guide and point clutch element to said magazine after such partsare placed in said casing,

spring means disposed in said casing for biasing said lead guide andpoint clutch element in a rearward direction, and

cooperating means on said casing and said clutch fingers for urging saidfingers into engagement with a lead rod positioned therebetween whensaid advancing clutch is moved forwardly in said casing.

2. The invention according to claim-9 wherein the forward ends of saidresilient fingers are pointed, and

said clutch fingers have internal lug portions having rearwardly facingshoulders receivable in said slots for cooperating with the ends of saidresilient fingers to guide said clutch fingers into said slots duringassembly of said pencil.

3. The invention according to claim 2 wherein the rearward ends of saidlug portions are longitudinally staggered,

whereby insertion of said tubular section into said advancing clutchcauses relative rotation between said tubular section and said clutch toalign said fingers with said slots.

4. The invention according to claim 1 wherein said advancing clutch isan integral, molded plastic part.

5. The invention according to claim 4 wherein the lead engaging surfacesof said fingers are semicylindrical.

1. In a mechanical pencil of the step-by-step propulsion type, thecombination comprising an elongated, integral, tubular casing having anecked down front end, a lead magazine element having a hollow,cylindrical main body portion for holding a plurality of lead rods and aforwardly extending, generally tubular section of reduced diameterprovided with a plurality of longitudinal slots extending to and openingat the forward end to provide a plurality of forwardly extendingresilient fingers, an advancing clutch including a collar surroundingsaid fingers and slidable thereon and having a plurality of leadengaging clutch fingers respectively disposed in said slots, an integrallead guide and point clutch element having an internal diameter largerthan but approximating the external diameter of said lead rods to permitsaid rods to slide therein and therethrough, said lead guide and pointclutch element being mounted in said casing forwardly of said advancingclutch and having an enlarged forward end including a plurality of pointengaging resilient jaws located forwardly of the front end of saidcasing, the external diameter of said enlarged forward end exceeding theinternal diameter of said necked down front end of said casing, therebypreventing the passage of said front end through said front end of saidcasing, the rear end of said lead guide and point clutch element beingsnap-fitted into the forward end of said resilient fingers with the holethrough said lead guide and point clutch in alignment with the holethrough said tubular section of said magazine to permit assembly of saidlead guide and point clutch element to said magazine after such partsare placed in said casing, spring means disposed in said casing forbiasing said lead guide and point clutch element in a rearwarddirection, and cooperating means on said casing and said clutch fingersfor urging said fingers into engagement with a lead rod positionedtherebetween when said advancing clutch is moved forwardly in saidcasing.
 2. The invention according to claim 9 wherein the forward endsof said resilient fingers are pointed, and said clutch fingers haveinternal lug portions having rearwardly facing shoulders receivable insaid slots for cooperating with the ends of said resilient fingers toguide said clutch fingers into said slots during assembly of saidpencil.
 3. The invention according to claim 2 wherein the rearward endsof said lug portions are longitudinally staggered, whereby insertion ofsaid tubular section into said advancing clutch causes relative rotationbetween said tubular section and said clutch to align said fingers withsaid slots.
 4. The invention according to claim 1 wherein said advancingclutch is an integral, molded plastic part.
 5. The invention accordingto claim 4 wherein the lead engaging surfaces of said fingers aresemicylindrical.